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Runyon classification of nontuberculous mycobacteria
| Class | Description | Growth | Pigment production | Main species |
|---|---|---|---|---|
| I | Photochromogens | Slow | Yellow-orange pigment when exposed to light | M. kansasii, M. marinum |
| II | Scotochromogens | Slow | Yellow-orange pigment with or without light | M. scrofulaceum, M.szulgai, M. gordonae |
| III | Nonchromogens | Slow | None | M. avium-intracellulare,M. xenopi, M. terrae |
| IV | Rapid growers (<7 days) | Rapid | None | M. fortuitum, M. chelonae M. abscessus |
